Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Causal diagram representing the assumed causal structure for a study population: A is the exposure, L is the set of measured confounders, U is the set of unmeasured risk factors, and Y is the outcome. The numbers represent visits over time.
